CATALYTIC MATERIALS FOR PYROLYSIS OF METHANE AND PRODUCTION OF HYDROGEN AND SOLID CARBON WITH SUBSTANTIALLY ZERO ATMOSPHERIC CARBON EMISSIONS
20220348460 · 2022-11-03
Inventors
Cpc classification
C01B32/05
CHEMISTRY; METALLURGY
International classification
Abstract
A catalyst for the pyrolysis of a hydrocarbon, such as methane or natural gas, includes a pile of waste-product configured to facilitate the decomposition of the hydrocarbon into hydrogen and carbon. The waste-product is one of bauxite residue, mill scale, or slag. The pile of waste product may be broken down into a powder or piece-meal form.
Claims
1-7. (canceled)
8. A method for producing hydrogen gas and solid carbon, comprising: passing a hydrocarbon over a waste-product catalyst; heating the hydrocarbon and waste-product catalyst; thermocatalytically decomposing the hydrocarbon into hydrogen and solid carbon; and collecting the hydrogen in a container.
9. The method for producing hydrogen gas and solid carbon of claim 8, wherein passing a hydrocarbon over a waste-product catalyst includes passing natural gas or methane over a waste-product catalyst.
10. The method for producing hydrogen gas and solid carbon of claim 8, further comprising collecting solid carbon deposited on the waste-product catalyst.
11. The method for producing hydrogen gas and solid carbon of claim 8, wherein passing a hydrocarbon over a waste-product catalyst includes passing the hydrocarbon over a catalytic pile of waste-product.
12. The method for producing hydrogen gas and solid carbon of claim 8, wherein passing a hydrocarbon over a waste-product catalyst includes passing the hydrocarbon over a waste-product catalyst that includes at least one of bauxite residue, slag, or mill scale.
13. The method for producing hydrogen gas and solid carbon of claim 11, wherein passing a hydrocarbon over a waste-product catalyst includes passing the hydrocarbon over a waste-product catalyst that includes: a substructure; and a layer of waste-product material as an outer layer on the substructure.
14. The method for producing hydrogen gas and solid carbon of claim 8, wherein the waste product catalyst is contained in a reactor.
15. The method for producing hydrogen gas and solid carbon of claim 13, wherein the reactor is a fixed bed, fluidized bed, moving bed, trickle bed, rotating bed, or slurry reactor.
16. The method for producing hydrogen gas and solid carbon of claim 8, further including a step of processing the waste product catalyst into a powder or piece-meal form.
17. The method for producing hydrogen gas and solid carbon of claim 8, wherein the hydrocarbon and waste product catalyst are heated from about 750° C. to about 950° C.
18. The method for producing hydrogen gas and solid carbon of claim 8, wherein the hydrocarbon and waste product catalyst are heated from about 500° C. to about 1300° C.
19. The method for producing hydrogen gas and solid carbon of claim 8, wherein passing a hydrocarbon over a waste-product catalyst includes passing the hydrocarbon over a waste-product catalyst that includes at least one of steel slag, copper slag, or nickel slag.
20. The method for producing a hydrogen gas and solid carbon of claim 11, wherein the slag is at least one of steel slag, copper slag, or nickel slag.
21. The method for producing hydrogen gas and solid carbon of claim 8, wherein the solid carbon is at least one of graphite or graphene.
22. The method for producing hydrogen gas and solid carbon of claim 8, wherein the waste-product is one of mill scale comprising at least about 40% to about 100% Fe.sub.2O.sub.3 by weight; or slag comprising at least one of: steel slag including about 22% to about 60% CaO by weight; nickel slag including about 30% to about 66% of FeO by weight; or copper slag including about 55% to about 70% Fe.sub.2O.sub.3 by weight.
23. The method for producing hydrogen gas and solid carbon of claim 22, wherein the waste-product is steel slag further including about 10% to about 35% FeO by weight.
24. The method for producing hydrogen gas and solid carbon of claim 22, wherein the waste-product is nickel slag further including: about 5% to about 8% SiO.sub.2 by weight; or about 32% to about 42% SiO.sub.2 by weight.
25. The method for producing hydrogen gas and solid carbon of claim 22, wherein the waste-product is copper slag further including: about 25% to about 35% SiO.sub.2 by weight.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] A better understanding of the features and advantages of the present disclosure will be obtained by reference to the following detailed description that sets forth illustrative aspects and the accompanying drawings of which:
[0028]
[0029]
[0030]
[0031]
[0032]
[0033]
DETAILED DESCRIPTION
[0034] Although the present disclosure will be described in terms of specific embodiments, it will be readily apparent to those skilled in this art that various modifications, rearrangements, and substitutions may be made without departing from the spirit of the present disclosure.
[0035] The description herein presents numerous specific details included to provide a thorough understanding of the present disclosure. It will be apparent, however, to one skilled in the art that the present disclosure can be practiced without some or all of these specific details. On the other hand, well-known process steps, procedures, and structures are not described in detail as to not unnecessarily obscure the present disclosure.
[0036] Production of pure hydrogen and solid carbon materials by the process of pyrolysis, or thermocatalytic decomposition, of methane is integral towards the development of a hydrogen economy. Improving the source and characteristics of catalysts used in the reaction is an important aspect of improving the feasibility of hydrogen production from natural gas or methane, the latter a principal component of natural gas. Enhancements in catalytic characteristics are generally made with respect to the reaction rate, minimizing operating temperatures, and the ability to retain thermochemical stability amid huge nanocarbon deposition. Accordingly, various metal and carbon-based catalysts were introduced. Metal-based catalysts are superior to carbon catalysts in terms of their hydrogen production percentage and reaction rate.
[0037] Transition metals, particularly Ni—, Fe—, and Co-based catalysts are often used to improve the catalytic reaction during pyrolysis. Ni-based catalysts are distinguished from the metal-based catalysts because of their relatively low-cost, low-toxicity, superior activity, stability, and environmentally friendly characteristics. Metal-based catalysts have a longer catalytic lifespan by upholding a nanocarbon formation mechanism which retains the active site of the metal on the top of the catalyst towards a reaction medium. The growth mechanism of nanocarbon or solid carbon products from the pyrolysis process involves the diffusion of deposited carbon through the active metal site. The diffused nanocarbons, then, precipitate on the other side of the metal particle to form longer carbon filaments.
[0038] The catalytic activity and stability of a catalyst used in the process and the characteristics of as produced nanocarbon are very relevant in thermocatalytic decomposition (TCD) since both play a vital role in determining the overall yield and structure of the solid carbon by-product and hydrogen produced. Solid carbon accumulates on the catalyst until the solid carbon saturates the catalyst thereby deactivating the catalyst. When the deactivation is nearly complete, the catalyst along with the solid carbon which it contains can be disposed of in a suitable manner or it can be used in other processes.
[0039] The solid carbon byproduct of the pyrolysis or TCD of methane is generally in the form of nanocarbons, graphitic carbons, or carbon nanotubes. This provides additional economic and, in some applications, environmental benefits (since it reduces the need to dispose of otherwise useless solid carbon) to producing hydrogen via pyrolysis or TCD. For example, the graphitic carbon by-products may be used for a variety of industrial and consumer applications, such as the production of pencil tips, high temperature crucibles, dry cells, electrodes, or as a lubricant, among many other applications known to those of ordinary skill in the art. Carbon nanotubes (CNTs) are cylinders of one or more layers, known as single-wall carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs) of graphene (lattice) of diameters between 0.8 to 2 nm for SWCNTs and 5 to 20 nm for MWCNTs. CNTs are structural materials of desirable properties and are used in applications including, but not limited to, energy storage, device modeling, automotive parts, boat hulls, sporting goods, water filters, thin-film electronics, coatings, actuators, and electromagnetic shields.
[0040] Providing low cost, environmentally friendly, and abundant catalytic materials mitigates the need for improving the characteristics of expensive catalytic materials or developing methods for re-using the catalysts.
[0041] The present disclosure describes a family of “waste-product” catalysts, or waste-products that form the catalytic material, which can promote the thermocatalytic decomposition (pyrolysis) of methane or natural gas into hydrogen and solid carbon and which may be used for low, about zero, or ‘negative’ carbon production of pure hydrogen. The catalysts are carbon neutral, allow for carbon consumption, and are environmentally friendly since they are composed of waste materials, which would have to be disposed of anyway. The waste-product catalysts are produced from the waste materials and allow for the pyrolysis or thermocatalytic decomposition (TCD) of methane at lower temperatures than when the catalysts are not used. Additionally, due to the abundance of these waste materials, replacing spent “waste-product” catalyst is economical and feasible since the material would otherwise be disposed of, for example, in a landfill. This thus mitigates the issue of solid carbon deposits building up on and deactivating the often more expensive catalytic material. Waste product catalysts may include slag, mill scale, bauxite residue or similar waste products that include sufficient levels of iron for TCD.
[0042] The waste-product catalysts serve to crack open the methane or natural gas. When these materials are used as waste-product catalysts in the TCD of methane, the following reaction takes place:
CH.sub.4.fwdarw.2H.sub.2+C ΔHo=75 kJ/mol (Equation 1)
[0043] With reference to
[0044] In the Bayer process, strip-mined bauxite ore is treated with sodium hydroxide, otherwise known as hot caustic soda, which selectively dissolves aluminum from an array of other mineralized metals. The end products are alumina (Al.sub.2O.sub.3), which is used to produce aluminum metals, and bauxite residue. For every ton of alumina produced approximately 1-1.5 tons of red mud is produced. Generally, the red mud produced is stored in ponds, has few other uses, and is not environmentally friendly. Given that the annual production of alumina, as of 2018, was approximately 126 million tons, resulting in the generation of 160 million tons of red mud, an appropriate and environmentally friendly use of red mud is desired.
[0045] Creating a waste-product catalyst out of red mud not only provides for efficient and effective pyrolysis to be performed but also re-purposes the waste-product from the Bayer process, reducing the environmental impact of both the pyrolysis process and the Bayer process. Further, the abundance of red mud makes it an attractive economical material for a catalyst.
[0046] Bauxite residue may be dried in various ways, such as kiln-dried or sun-dried, and subsequently processed to form a “powder” or “piece-meal” (small chunks and pieces) catalytic pile. The dried red mud may be placed into and contained by a chemical reactor for pyrolysis. The reactor may be a fixed bed, fluidized bed, moving bed, trickle bed, rotating bed, or slurry reactor. Any suitable reactor known by those of ordinary skill in the art of chemical reactors or pyrolysis may be used. Placing the dried red mud catalytic pile directly into the chemical reactors, in addition to the carbon savings and hydrogen production, reduces the cost of producing catalytic materials, as no further processing of the catalyst is required.
[0047] In aspects, a waste-product catalyst may include a catalytic substructure coated with a layer of refined or dried red mud. In aspects, the substructure may be made from red mud and dried red mud may then be layered onto the catalytic substructure. The dried red mud may be configured to form the whole of the catalytic structure. In aspects, Nickel (Ni), Cobalt (Co), or Iron (Fe) metals or compounds may be added to the red mud to enhance catalytic performance of the red mud.
[0048] The bauxite residue may contain 30-60 wt % of iron (III) oxide (Fe.sub.2O.sub.3), 10-20 wt % of aluminum oxide (A;.sub.2O.sub.3), 3-50 wt % of silicon dioxide (SiO.sub.2), 2-10 wt % of sodium oxide (Na.sub.2O), 2-8 wt % of calcium oxide (CaO), and about 0-25 wt % of titanium dioxide (TiO.sub.2). Additionally, trace amounts of MgO are often found in red mud. Al.sub.2O.sub.3, SiO.sub.2, MgO, and TiO.sub.2 are known in the art to improve catalytic performance as discussed in the journal Renewable & Sustainable Energy Reviews March 2017 article titled: “A review on methane transformation to hydrogen and nanocarbon: Relevance of catalyst characteristics and experimental parameters on yield,” by Ashik et. al. In particular, SiO.sub.2 as a catalyst additive is an effective material for enhancing the catalytic reaction in pyrolysis. Thus, dried bauxite residue in a “powder” or “piece-meal” pile is a desirable catalytic material.
[0049] The red mud may be refined to include desirable quantities of its respective components. The red mud may be layered on a substructure including Co, Ni, Fe, or metal oxides, such as Al.sub.2O.sub.3 or MgO. The catalytic substructure may be of any shape, size, or geometry as known by those of ordinary skill in the art. The catalytic substructure may be a cylinder, cube, bar, honeycomb, or any other desirable shape.
[0050] In another aspect of this disclosure, a waste-product catalyst includes solid particles or flakes originating as waste material from the production and processing of steel and is composed of steel without any admixtures. In aspects, the solid particles or flakes may be mill scale produced as a by-product from steel rolling processes. Mill scale is the flaky surface or thin iron oxide layer of hot rolled steel and is comprised of mixed iron oxides such as iron (II) oxide (FeO), iron (III) oxide (Fe.sub.2O.sub.3), and iron (II-III) oxide (Fe.sub.3O.sub.4, magnetite). In aspects, the mill scale waste material may be composed of about 40% to about 100% Fe.sub.2O.sub.3 or about more than 90% Fe.sub.2O.sub.3. The mill scale is collected into catalytic piles and placed in a suitable reactor, such as a fixed bed, fluidized bed, moving bed, trickle bed, rotating bed, or slurry reactor. Any suitable reactor known by those of ordinary skill in the art of chemical reactors or pyrolysis may be used.
[0051] In another aspect of this disclosure, slag, a waste-material that is a by-product left over after a metal has been separated from its raw ore may be used as all, or a portion of, the waste-product catalyst. The slag is collected into catalytic piles to form the waste-product catalyst. The slag may be broken clown into “powder” or “piece-meal” form and collected into catalytic piles. The catalytic piles of slag are placed in a suitable reactor as described above regarding mill scale and red mud.
[0052] Slag is generally composed of a mixture of metal oxides and silicon dioxide (SiO2), but may also include metal sulfides, magnesium oxide (MgO), and other elemental metals. Typical compositions for various types of slag are shown in Table 1:
TABLE-US-00001 TABLE 1 Blast Electric arc furnace slag Type furnace Converter Oxidizing Reducing Component slag slag slag slag CaO 41.7 45.8 22.8 55.1 SiO2 33.8 11.0 12.1 18.8 T-Fe 0.4 17.4 29.5 0.3 MgO 7.4 6.5 4.8 7.3 Al.sub.2O.sub.3 13.4 1.9 6.8 16.5 S 0.8 0.06 0.2 0.4 P.sub.2O.sub.5 <0.1 1.7 0.3 0.1 MnO 0.3 5.3 7.9 1.0
[0053] The slag may be steel slags produced, for example, in the steel industry during the purification of crude iron (also called pig iron). The purification of crude iron is often done in a basic oxygen furnace (BOF) or electric arc furnace (EAF) in order to oxidize the various residual gangues which are separated by floating on the iron melt. Table 2 shows exemplary compositions by percent weight (wt %) of steel slag produced using a BOF or a EAF.
TABLE-US-00002 TABLE 2 EAF wt % Components BOS wt % (Carbon Steel) FeO 10-35 15-30 CaO 30-55 35-60 SiO.sub.2 8-20 9-20 Al.sub.2O.sub.3 1-6 2-9 MgO 5-15 5-15 MnO 2-8 3-8 P.sub.2O.sub.5 0.2-2 0.01-0.25 S 0.05-0.15 0.08-0.2 Cr 0.1-0.5 0.1-1
[0054] In aspects, the slag may be Nickel slag (Ni slag). Ni slag is produced as waste material in the production of nickel metals. Nickel ore, which may be pentlandite mixed with Fe and S as (Ni,Fe).sub.9S.sub.8 is smelted to procude a nickel matte. The nickel matte includes Nickel and iron sulfide. The nickel matte is then processed in an electric furnace where the iron in the nickel matte is oxidized and the iron may be combined with silica to produce a slag containing about 30%, or less, to about 40 wt %, or more, of FeO. A converter furnace may further purify the Nickel matte from iron oxides still in the nickel matte to produce a slag containing about 60%, or less, to about 66%, or more, of FeO. Table 3 shows exemplary compositions of Ni Slags.
TABLE-US-00003 TABLE 3 Electric converter Components furnace wt % furnace wt % FeO 32-40 60-66 Fe.sub.2O.sub.3 2-7 13-18 CaO 3-6 7-9 SiO.sub.2 32-42 5-8 Al.sub.2O.sub.3 7-12 0.5-1.5 Cr.sub.2O.sub.3 2-3 1-5 MgO 3-6 5-8
[0055] In other aspects, the slag may be Copper Slag (Cu Slag) that is produced as a waste material in the smelting process of a copper ore that exists, for example, as copper iron sulfate (e.g., CuFeS.sub.2 or Cu.sub.5FeS.sub.4), that produces a copper matte. The copper matte is then processed to remove the iron, sulfur, and gangue material from the copper matte. Silica may be added to the smelt as the silica interacts with iron oxides of the copper matte to form a floating layer that can be separated from the smelt. The iron oxides mixed with silica form the Copper slag. Table 4 shows exemplary compositions of Cu Slags.
TABLE-US-00004 TABLE 4 Components wt % F.sub.2O.sub.3 55-70 Al.sub.2O.sub.3 0.5-5 SiO.sub.2 25-35 CaO 0.15-6
[0056] In aspects, slag or mill scale may be layered onto a catalytic substructure or form the entirety of the catalytic substructure. In aspects, a catalytic substructure may include multiple layers of slag and/or mill scale.
[0057] In another aspect of this disclosure, raw iron ore, while not a waste product, is broken into “powder” or “piece-meal” form and collected into catalytic piles for use in a chemical reactor for pyrolysis. Iron ore is generally mined for the extraction of its iron used to make steel and is typically not a waste product, but rather the raw material processed into a future product. Iron ore is a cheaper material compared to many standard catalysts in its unprocessed state. Slag and mill scale are the remains or waste product of the iron ore after it has been processed.
[0058] Slag, mill scale, and red mud provide attractive materials for creating waste-product catalysts for pyrolysis since they are materials that already require disposal and have desirable properties for pyrolysis. Table 5 below provides a comparison of the carbon accumulation ratios of red mud and mill scale versus typical catalytic materials. The higher the ratio of grams (g) of carbon per grams (g) of catalyst, the more hydrogen is produced since at the higher ratios more of the carbon is separated from the hydrocarbon (e.g., methane) and accumulated on the catalyst. The amount of carbon accumulated over the waste product catalysts, (red mud and mill scale), compares favorably to those catalysts that are conventionally used. Notably, the carbon accumulation ratio of mill scale exceeds many other catalysts.
TABLE-US-00005 TABLE 5 Catalyst Carbon accumulation (Prior Art = “PA”) Pyrolysis conditions (g carbon/g catalyst) Iron Oxide (PA) 100% CH4 @ 800° C. 0.5 Iron/Aluminum (PA) 30% CH4 @ 700° C. 0.8 Iron/Aluminum (PA) 100% CH4 @ 750° C. 1.9 Iron/Ceria (PA) 30% CH4 @ 750° C. 4.1 Iron/Lanthana (PA) 100% CH4 @ 800° C. 8.9 Iron/Ceria (PA) 100% CH4 @ 800° C. 9.6 Red mud 100% CH4 @ 900° C. 1.7 Mill scale 100% CH4 @ 900° C. 9.5
[0059] With reference to
[0060] With reference to
[0061] In another aspect of this disclosure, a method 500 for the production of hydrogen from a hydrocarbon, such as methane or natural gas, includes a step 510 of passing a hydrocarbon over a waste-product catalyst of this disclosure. At step 520, the method includes heating a hydrocarbon in the presence of a waste-product catalyst of the present disclosure to a desirable temperature. In aspects, the hydrocarbon may be heated from 500° C. to about 1300° C. In aspects, the hydrocarbon and waste-product catalyst are heated from about 750° C. to about 950° C. In another step 530, the hydrocarbon (e.g., methane) is decomposed into pure hydrogen and solid carbon. The method includes producing solid carbon on the surface of the waste-product catalyst. In aspects, only solid carbon, and not gaseous carbon, is produced as a by-product. In another step 540, the method includes collecting the hydrogen in a container. The method may include using the produced hydrogen to heat the catalyst. In another step 550, the method includes collecting the solid carbon from the waste-product catalyst. In aspects, the waste-product catalyst is a catalytic pile including at least one of red mud, mill scale, or slag. In aspects, the solid carbon and waste-product catalyst is disposed of in the ground to prevent carbon from escaping into the atmosphere.
[0062] With reference to
[0063] Certain aspects of the present disclosure may include some, all, or none of the above advantages and/or one or more other advantages readily apparent to those skilled in the art from the drawings, descriptions, and claims included herein. Moreover, while specific advantages have been enumerated above, the various aspects of the present disclosure may include all, some, or none of the enumerated advantages and/or other advantages not specifically enumerated above.
[0064] The phrases “in an aspect,” “in aspects,” “in various aspects,” “in some aspects,” or “in other aspects” may each refer to one or more of the same or different aspects in accordance with the present disclosure. A phrase in the form “A or B” means “(A), (B), or (A and B).” A phrase in the form “at least one of A, B, or C” means “(A); (B); (C); (A and B); (A and C); (B and C); or (A, B, and C).”
[0065] It should be understood the foregoing description is only illustrative of the present disclosure. Various alternatives and modifications can be devised by those skilled in the art without departing from the disclosure. Accordingly, the present disclosure is intended to embrace all such alternatives, modifications, and variances. The aspects described with reference to the attached drawing figures are presented only to demonstrate certain examples of the disclosure. Other elements, steps, methods, and techniques that are insubstantially different from those described above and/or in the appended claims are also intended to be within the scope of the disclosure.